Semiconductor material having an equilibrium dopant solubility

Abstract

A method for enhancing the equilibrium solid solubility of dopants in silicon, germanium and silicon-germanium alloys. The method involves subjecting silicon-based substrate to biaxial or compression strain. It has been determined that boron solubility was largely enhanced (more than 100%) by a compressive bi-axial strain, based on a size-mismatch theory since the boron atoms are smaller than the silicon atoms. It has been found that the large enhancement or mixing properties of dopants in silicon and germanium substrates is primarily governed by their, and to second order by their size-mismatch with the substrate. Further, it has been determined that the dopant solubility enhancement with strain is most effective when the charge and the size-mismatch of the impurity favor the same type of strain. Thus, the solid solubility of small p-type (e.g., boron) as well as large n-type (e.g., arsenic) dopants can be raised most dramatically by appropriate bi-axial (compressive) strain, and that solubility of a large p-type dopant (e.g, indium) in silicon will be raised due to size-mismatch with silicon, which favors tensile strain, while its negative charge prefers compressive strain, and thus the two effects counteract each other.

What is claimed is:  
     
         1 . A semiconductor material having an equilibrium dopant solubility of greater than 1%, said dopant being selected from the group of dopants consisting of a p-type with small atoms compared to the semiconductor material, and n-type with large atoms compared to the semiconductor materials.  
     
     
         2 . The material of  claim 1 , wherein the p-type dopant is boron and the semiconductor material is from the group consisting of silicon, (Si), germanium(Ge), silicon germanium alloys (Si x Ge 1-x ), silicon on zinc-sulfite (ZnS), Si x Ge 1-x  alloy on silicon, Si x Ge 1-x  alloy on ZnS, Si x Ge 1-x  alloy on AlP, and Si x Ge 1-x  alloy on Si y Ge 1-y  alloy, wherein x and y refer to different compositions of the silicon germanium alloys, with x smaller than y.  
     
     
         3 . The material of  claim 1 , wherein the n-type dopant is arsenic, phosphorous and antimony, and the semiconductor material is silicon (Si), germanium(Ge), silicon germanium alloys (Si x Ge 1-x ), silicon on aluminum-phosphate(AlP), silicon on Si x Ge 1-x  alloy, and Si x Ge 1-x  alloy on Si y Ge 1-y  alloy, wherein x and y refer to different compositions of the silicon germanium alloys, with x larger than y.